Right atrial MR imaging studies of cadaveric atrial casts and comparison with right and left atrial volumes and function in healthy subjects.

Abstract

To assess magnetic resonance (MR) imaging of the right atrium by measuring volumes of right atrial casts and determining right atrial volume cycles in healthy subjects. Fourteen human cadaveric atrial casts were imaged and right atrial volumes of eight subjects were measured with cardiac-gated cine MR. Volumes were calculated and right and left atrial volumes were compared. Measured volumes of right atrial casts correlated well (r = .99, P < .001) with true volumes with a small underestimation noted (-7.2 mL +/- 2.3 [standard deviation], P < .001). The maximum in vivo right atrial volume averaged 77 mL/m2 +/- 11 of body area. The right atrial reservoir and conduit functions accounted for, on average, 58% and 19%, respectively, of the ventricular stroke volume; the remaining 23% came from atrial contraction. Right-to-left peak volume ratio averaged 1.41 +/- 0.15 (P < .001), and all volume measurements except conduit volumes were statistically significantly larger in the right atrium than the left. MR imaging provides a reliable means to study right atrial volumes and phasic function.